This disclosure is directed to coated granular fertilizers, their methods of manufacture, and methods of use.
Granular fertilizers can be coated to reduce dust production and to slow the release of nutrients into the soil. However, commercial products such as sulfur-coated urea, polyurethane-coated urea, and polyethylene coated-urea have certain drawbacks. For example, sulfur coatings can increase the acidity of soil by forming sulfuric acid upon degradation of the coating. Because the sulfur coatings and the polyethylene coatings generally do not contain nitrogen, the overall nitrogen content of the fertilizer on a weight basis is decreased. The polyurethane and the polyethylene coatings are not readily biodegradable, and thus only partially decompose or do not decompose at all. These coating materials or the residues thereof can therefore accumulate in soil over time, with potentially adverse results. Accordingly, improved fertilizer coatings are continuously sought, in particular fertilizer coatings that are biodegradable. It would be a further advantage if the fertilizer coatings did not adversely affect soil conditions over time, and it would be an even further advantage if a high weight basis of nitrogen was maintained.